Outline the six horizons in a soil profile and briefly describe four of the six.
A soil profile is a description of soil textures in different horizons or layers. A complete soil profile contains six basic layers, which each layer represented by a letter. See the diagram below which was taken from the following website: http://www.enchantedlearning.com/geology/soil/
Note: I had space, so I briefly described all 6 layers.
The O-Horizon layer is the top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter). The O-Horizon layer is more evident in forest soils than agricultural soils because of the leaf litter found in forest soils. The A-Horizon layer is composed of topsoil consisting of a mixture of humus and mineral soil. Many shallow-rooted plants are concentrated in this layer. The E-Horizon layer is composed mostly of sand and silt, and is lighter in color than the O or A layers, having lost most of the clay, minerals, and humus through a process called “eluviation”, as water drips through the soil. The B-Horizon layer, or subsoil layer, contains the clay and mineral deposits that have leached out of the A and E Horizon layers. According to our text book, this layer of “translocated soil components” is also known as the “illuviation” layer. Subsoils in this layer that are high in build-up of clay are poorly drained, which adversely affects the growth of plants with deep root systems. The C-Horizon layer consists of slightly broken-up bedrock. Very little organic material makes its way into this layer, and neither do plant roots penetrate this layer. The R-Horizon layer is un-weathered bedrock composed primarily of granite, limestone, and sandstone. It is worth noting that not all soils have all six layers.
Works Cited/Consulted:
Burton, D.L. (2008). Introduction to Forestry Science, Second Ed. Thompson Delmar Learning. Pg 91-94....
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